fix(active): Taps/clicks now use .activated instead of .active, closes #913

Both .active and .activated classes exist within the css now. When a
button/link/item is “active”, the .activated class gets added and
removed. This is so Ionic is not removing any user defined .active
classes, but also so users can use Ionic’s active classes (but not have
to worry about them being removed automatically by Ionic). Styled the
same by default, but easily overridden.